//https://www.nowcoder.com/practice/d77d11405cc7470d82554cb392585106?tpId=13&&tqId=11174&rp=1&ru=/activity/oj&qru=/ta/coding-interviews/question-ranking
//栈的压入弹出

bool IsPopOrder(vector<int>& pushV, vector<int>& popV) {
        // write code here
        stack<int> st;
        size_t i = 0;
        for(auto e : pushV)
        {
            st.push(e);
            while(i < popV.size() && !st.empty() && st.top() == popV[i])
            {
                st.pop();
                i++;
            }
        }

        return st.empty();
    }

   